The preparation of molded articles such as phenolics, melamines and silicones by transfer molding is known and has become popular as a molding technique for certain parts and articles having intricate sections as well as molded inserts and those requiring close tolerances, as well as reduced mold cycle times. Generally the term transfer molding as referred to in the literature is applied to a process of forming articles in a closed mold from a thermosetting reaction mixture that is conveyed, usually under pressure, from an auxiliary chamber or pot. The various types of transfer molding known in the art are generally referred to as the pot type and include plunger molding using cams, transfer molding in a compression press and screw transfer molding. Transfer molding (referred to in the trade as Resin Transfer Molding or RTM) and its various intricacies and advantages are described for example in the Plastics Engineering Handbook, 4th Edition, pp 220-240, Van Nostrand Reinhold Co. and incorporated herein by reference.
The preparation of polyisocyanurate foams using a wide variety of trimerization catalysts has been suggested and used (See, for example U.S. Pat. No. 4,033,908 and references cited therein).
U.S. Pat. Nos. 3,878,156, 3,883,466 and 3,886,102 all describe the preparation of rigid polyurethane compositions from polyether polyols, isocyanates, organic carbonates and non-amine containing metallic catalysts.
U.S. Pat. No. 4,035,331 discloses a rigid non-cellular polyurethane composition using an amine initiated polyol, an isocyanate and a liquid modifier of an organic carbonate.
U.S. Pat. No. 3,703,520 describes the preparation of an insoluble trimerization adduct catalyst of ethylene carbonate and triethylene diamine.